4. A Taiwanese junior high school teacher preparing students for an English speech contest requires learners to repeat sentence patterns multiple times until pronunciation, grammar, and intonation are produced accurately. The teacher believes that language proficiency develops when correct responses are reinforced and errors are corrected immediately before they become habitual.

Which underlying theoretical assumption BEST explains this instructional approach?
(A) Language is acquired primarily through social interaction and collaborative meaning- making
(B) Language acquisition is facilitated when learners experience low levels of anxiety and heightened suggestibility
(C) Language develops naturally when learners construct knowledge independently
(D) Language learning involves the formation of automatic habits through stimulus-response practice and reinforcement